Terni, city, capital of Terni provincia, Umbria regione, central Italy. It lies along the Nera River, north of Rome. The city was founded on the site of the ancient city of Interamna Nahars and in the 14th century became a dominion of the papacy. Terni’s important archaeological remains include a Neolithic village, cemeteries of the Villanovan period, and a Roman amphitheatre and walls. Its 12th-century cathedral, built on an earlier site, was extensively remodeled in the 17th century. The 5th-century round Church of San Salvatore, with a 12th-century chapel, was erected over a Roman building, possibly a temple of the Sun. The city’s other medieval churches include San Francesco, with a bell tower from 1345. A notable secular monument is the Renaissance-style Spada Palace, the last work of Antonio da Sangallo the Younger, who died at Terni in 1546. The chief local attraction is the Cascata delle Marmore, a waterfall created by the Roman consul Manius Curius Dentatus (271 bc) by diverting the waters of the Velino River into the Nera. The waters now provide hydroelectric power.
Although half of Terni was destroyed in World War II, it reemerged larger and more active, with modern industrial plants and a growing service sector. Metallurgy and the manufacture of arms, machinery, textiles, electrochemicals, and food products are important. Pop. (2000 est.) mun., 222,859.